DISRUPTIVE DISCHARGE — DIFFERENCE OF POSITIVE AND NEGATIVE DISCHARGE. 127 



alone occurred up to 0'40 ; then spark and brush at 0*42 ; whilst from 0*44 and up- 

 wards tlie noisy negative brush alone took place. 



1488. We thus find a great difterence as the balls are rendered inductric or induc- 

 teous ; the small ball rendered positive inducteously giving a spark nearly twice as 

 long as that produced when it was charged positive inductrically, and a similar dif- 

 ference, though not, under the circumstances, to the same extent, was manifest when 

 it was rendered negative. 



1489. Another result is, that the small ball rendered positive gives a much longer 

 spark than when it is rendered negative, and that the small ball rendered negative 

 gives a brush more readily than when positive, in relation to the effect of increasing 

 distance. 



1490. When the interval was below 0*4 of an inch, so that the small ball should 

 give sparks, whether positive or negative, I could not observe that there was any 

 constant difference, either in their ready occurrence or the number which passed in 

 a given time. But when the interval was such that the small ball when negative 

 gave a brush, then the discharges from it, as separate negative brushes, were far 

 more numerous than the corresponding discharges from it when rendered positive, 

 whether those positive discharges were as sparks or brushes. 



1491. It is, therefore, evident that, when a ball is discharging electricity in the 

 form of brushes, the brushes are far more numerous, and each contains or carries off 

 far less electric force when the electricity so discharged is negative, than when it is 

 positive. 



1492. In all such experiments as those described, the point of change from spark 

 to brush is very much governed by the working state of the electrical machine and 

 the size of the conductor connected with the discharging ball. If the machine be in 

 strong action and the conductor large, so that much power is accumulated quickly 

 for each discharge, then the interval is greater at which the sparks are replaced by 

 brushes ; but the general effect is the same. 



1493. These results, though indicative of very striking and peculiar relations of 

 the electric force or forces, do not show the relative degrees of charge which the 

 small ball acquires before discharge occurs, i. e. they do not tell whether it acquires 

 a higher condition in the negative, or in the positive state, immediately preceding 

 that discharge. To illustrate this important point I arranged two places of dis- 

 charge as represented, fig. 16. A and D, are brass balls 2 inches in diameter, 

 B and C are smaller brass balls 0*25 of an inch in diameter ; the forks L and R sup- 

 porting them were of brass wire 0*2 of an inch in diameter : the space between the 

 large and small ball on the same fork was 5 inches, that the two places of discharge 

 n and o might be sufficiently removed from each other's influence. The fork L was 

 connected with a projecting cylindrical conductor, which could be rendered positive 

 or negative at pleasure, by an electrical machine, and the fork R was attached to 

 another conductor, but thrown into an uninsulated state by connection with a dis- 



